Permeability and electrokinetic characterization of poly(ethylene terephthalate) capillary pore membranes with grafted temperature-responsive polymers
Permeability and electrokinetic characterization of poly(ethylene terephthalate) capillary pore membranes with grafted temperature-responsive polymers
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DOI：
10.1021/la0603774
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发表时间：
2007-01-02
期刊：
影响因子：
3.9
通讯作者：
Ulbricht, Mathias
中科院分区：
文献类型：
--
作者：
Geismann, Christian;Yaroshchuk, Andriy;Ulbricht, Mathias
采用单体N-异丙基丙烯酰胺(NIPAAm)和光引发的接枝方法对平均孔径分别为692 nm和1629 nm的聚对苯二甲酸乙二酯(PET)径迹蚀刻膜进行功能化处理，其中通过将未经修饰的PET表面与二苯甲酮以及胺化的PET表面与二苯甲酮羧酸相结合，最有效地实现了表面选择性反应。只有在较高离子强度的水溶液(例如0.1M氯化钠)测量的渗透率的基础上，才能一致地估计基础PET膜的孔径和PET孔壁上的有效接枝聚NIPAAm层厚度。然而，用超纯水测量的渗透系数表明，两种基膜的“电粘性效应”都是显著的。膜孔径、表面电荷和溶液离子强度的影响可以在空间电荷模型的框架内得到解释。通过跨膜流动电位测量估算，具有折叠接枝聚合物水凝胶层厚度为几纳米的功能化膜的Zeta电位值几乎为零。这是由中性水凝胶对表面电荷的“流体动力学筛选”造成的。测试了具有接枝聚NIPAAm层的PET膜的渗透性随温度的显著变化，溶胀状态下的有效层厚度高达300 nm，与官能化程度很好地相关。在25℃时，溶液离子强度对流体动力层厚度的细微附加影响不同于基础PET膜的影响，可以通过溶胀度的变化来解释，类似于“盐析”效应。总体而言，已经证明，功能化毛细孔膜非常适合于详细和定量地评估接枝的刺激响应聚合物层的合成、结构和功能之间的关系。
Poly(ethylene terephthalate) (PET) track-etched membranes with average pore diameters of 692 and 1629 nm were functionalized using the monomer N-isopropylacrylamide (NIPAAm) and a photoinitiated "grafting-from" approach in which a surface-selective reaction has been most efficiently achieved by combinations of the unmodified PET surface with benzophenone and, alternatively, of an aminated PET surface with benzophenone carboxylic acid. Consistent estimations of the pore diameters of the base PET membranes and of the effective grafted polyNIPAAm layer thicknesses on the PET pore walls were possible only on the basis of the permeabilities measured with aqueous solutions of higher ionic strength (e.g., 0.1 M NaCl). However, the permeabilities measured with ultrapure water indicated that the "electroviscous effect" was significant for both base membranes. The influences of membrane pore diameter, surface charge, and solution ionic strength could be interpreted in the framework of the space-charge model. Functionalized membranes with collapsed grafted polymer hydrogel layer thicknesses of a few nanometers exhibited almost zero values of the zeta potential estimated from the trans-membrane streaming potential measurements. This was caused by a "hydrodynamic screening" of surface charge by the neutral hydrogel. Very pronounced changes in permeability as a function of temperature were measured for PET membranes with grafted polyNIPAAm layers, and the effective layer thickness in the swollen statehere up to similar to 300 nmcorrelated well with the degree of functionalization. The subtle additional effects of solution ionic strength on the hydrodynamic layer thickness at 25 degrees C were different from the effects for the base PET membranes and could be explained by a variation in the degree of swelling, resembling a "salting-out" effect. Overall, it had been demonstrated that the functionalized capillary pore membranes are well suited for a detailed and quantitative evaluation of the relationships between the synthesis, the structure, and the function of grafted stimuli-responsive polymer layers.